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Abstract:

A multiband dipole antenna solution suitable for use in various wireless
device applications, and methods of tuning and utilizing the same. In one
embodiment, the antenna is adapted for use in long term evolution (LTE or
LTE-A) radio devices. In one implementation, the antenna comprises (i)
two planar directly fed radiating elements operating in a lower frequency
band and disposed on two opposing sides of a dielectric structure, and
(ii) two electromagnetically coupled radiating elements operating in an
upper frequency band also disposed on the opposing sides of the
dielectric structure. An additional pair of electromagnetically coupled
radiator elements is utilized to achieve wider antenna operating
bandwidth.

Claims:

1. An antenna apparatus operable in a first frequency band and a second
frequency band, the apparatus comprising: a dielectric element comprising
a first side and a second side, a feed point disposed on the first side,
and a ground point disposed on the second side; a first structure
operable in the first frequency band and disposed substantially on the
first side; a second structure operable in the first frequency band and
disposed substantially on the second side; a third structure operable in
the second frequency band and disposed substantially on the first side;
and a fourth structure operable in the second frequency band and disposed
substantially on the second side; wherein: the first structure is
galvanically coupled to the feed point; and the second structure is
galvanically coupled to the ground point.

2. The antenna apparatus of claim 1, wherein the third structure is
configured to form an electromagnetic coupling to the first structure,
and the fourth structure is configured to form an electromagnetic
coupling to the second structure.

4. The antenna apparatus of claim 3, further comprising: a first
substantially linear conductive element disposed on the first side and
configured to couple the feed point to the first and the second radiator
arms via a first T-junction; and a second substantially linear conductive
element disposed on the second side and configured to couple the feed
point to the third and the fourth radiator arms via a second T-junction.

5. The antenna apparatus of claim 3, wherein the first radiator arm and
the second radiator arm each comprise a linear slot disposed
substantially longitudinally within the respective arm.

6. The antenna apparatus of claim 1, further comprising: a first
conductive element disposed between the first structure and the feed
point and effecting the galvanic coupling to the feed point; a first
electromagnetic coupling element electrically disposed between the first
conductive element and a first branch of the third structure; and a
second electromagnetic coupling element electrically disposed between the
first conductive element and a second branch of the third structure;
wherein: the first electromagnetic coupling element is configured to
electromagnetically couple the first branch of the third structure to the
feed point; and the second electromagnetic coupling element is configured
to electromagnetically couple the second branch of the third structure to
the feed point.

7. The antenna apparatus of claim 6, further comprising: a second
conductive element disposed between at least a portion of the second
structure and the ground point, and effecting the galvanic coupling to
the ground point; a third electromagnetic coupling element electrically
disposed between at least a portion of the second conductive element and
a first branch of the fourth structure; and a fourth electromagnetic
coupling element electrically disposed between at least a portion of the
second conductive element and a second branch of the fourth structure;
wherein: the third electromagnetic coupling element is configured to
electromagnetically couple the first branch of the fourth structure to
the ground point; and the fourth electromagnetic coupling element is
configured to electromagnetically couple the second branch of the fourth
structure to the ground point.

8. The antenna apparatus of claim 7, further comprising a coupling
structure disposed substantially on the first side and configured to
electrically couple to the second conductive element.

9. The antenna apparatus of claim 8, electric coupling of the coupling
structure to the second conductive element is effected via a conductor
that penetrates through the dielectric element in a direction normal to
the first side.

10. The antenna apparatus of claim 1, wherein the first structure and the
second structure are configured to cooperate to form at least a portion
of a first dipole antenna operable in the first frequency band; and the
third structure and the fourth structure are configured to cooperate to
form at least a portion of a second dipole antenna operable in the second
frequency band.

11. The antenna apparatus of claim 10, wherein the antenna apparatus is
characterized by a substantially omni-directional radiation pattern in at
least one of the first frequency band and the second frequency band, in a
plane substantially normal to the dielectric element.

12. The antenna apparatus of claim 10, wherein antenna operation in the
second frequency band is effected at least in part by a higher mode
resonance in the first frequency band.

13. The antenna apparatus of claim 10, wherein: the first frequency band
comprises a lower frequency long term evolution (LTE) application band;
and the second frequency band comprises an upper frequency LTE
application band.

14. A multiband antenna component for use with a radio communications
device, the antenna operable in a first frequency band and a second
frequency band, the antenna component comprising: a dielectric element
comprising a first side and a second side; a first structure operable in
the first frequency band and disposed substantially on the first side; a
second structure operable in the first frequency band and disposed
substantially on the second side; wherein: the first structure is
connected to a feed disposed on the first side; and the second structure
is connected to a coupling.

15. The antenna component of claim 14, further comprising: a third
structure operable in the second frequency band and disposed
substantially on the first side; and a fourth structure operable in the
second frequency band and disposed substantially on the second side;
wherein: the third structure is configured to electromagnetically couple
to the first structure; and the fourth structure is configured to
electromagnetically couple to the second structure.

16. The antenna component of claim 15, wherein the first frequency band
comprises a lower frequency long term evolution (LTE) application band
and second frequency band is selected from a group consisting of (i)
1710-1990 MHz, (ii) 2110-2170 MHz; and 2500-2700 MHz.

17. The antenna component of claim 15, wherein: the first structure
comprises a first radiator arm disposed substantially co-planar with yet
parallel to a second radiator arm; and the second structure comprises a
third radiator arm disposed substantially co-planar with yet parallel to
a fourth radiator arm.

18. The antenna component of claim 17, wherein: the first radiator arm
comprises a first linear slot disposed substantially longitudinally
within the first radiator arm; and the second radiator arm comprises a
second linear slot disposed substantially longitudinally within the
second radiator arm.

19. The antenna component of claim 17, further comprising: a first
conductive element disposed between the first structure and the feed
point and effecting the connection of the first structure to the feed
point; a first electromagnetic coupling element electrically disposed
between the first conductive element and a first branch of the third
structure; and a second electromagnetic coupling element electrically
disposed between the first conductive element and a second branch of the
third structure; wherein: the first electromagnetic coupling element is
configured to electromagnetically couple the first radiator arm to the
feed; and the second electromagnetic coupling element is configured to
electromagnetically couple the second radiator al to the feed.

20. The antenna component of claim 15, further comprising: a first
conductive element disposed on the first side and configured to effect
the connection between the feed and the first structure; and a second
conductive element disposed on the second side and configured to effect
the connection between the coupling and the second structure.

21. The antenna component of claim 20, further comprising a structure
disposed substantially on the first side and configured to electrically
couple to the second conductive element.

22. The antenna component of claim 15, wherein: outer perimeter of the
first structure is configured substantially external to outer perimeter
of the second structure; and outer perimeter of the third structure is
configured substantially external to outer perimeter of the fourth
structure.

23. The antenna component of claim 15, wherein: outer perimeter of the
first structure is configured to overlap at least partially outer
perimeter of the third structure when viewed in a direction substantially
normal to the first side; and outer perimeter of the second structure is
configured to overlap at least partially outer perimeter of the fourth
structure when viewed in the direction substantially normal to the first
side.

24. The antenna component of claim 15, further comprising: a fifth
structure disposed substantially on the first side and configured to
electromagnetically couple to the second structure; and a sixth structure
disposed substantially on the second side and configured to
electromagnetically couple to the first structure.

25. A method of enabling radio communications device operation using a
multiband dipole antenna, the method comprising: providing a feed signal
to a feed disposed on a first side of a dielectric substrate, and to a
coupling disposed on the second side of the dielectric substrate;
exciting a first antenna structure disposed substantially on the first
side and electrically coupled to the feed so as to radiate in a first
frequency band; and exciting a second antenna structure disposed
substantially on the second side so as to radiate in the first frequency
band.

26. The method of claim 25, further comprising: causing a third antenna
structure, disposed substantially on the first side, to radiate in a
second frequency band different than the first band by effecting
electromagnetic coupling between the third antenna structure and the
first antenna structure in the second frequency band; and causing a
fourth antenna structure, disposed substantially on the second side, to
radiate in the second frequency band by effecting electromagnetic
coupling between the fourth antenna structure and the second antenna
structure in the second frequency band.

27. The method of claim 25, wherein: the first antenna structure
comprises a first radiator arm disposed substantially co-planar with yet
parallel to a second radiator arm; and the second antenna structure
comprises a third radiator arm disposed substantially co-planar with yet
parallel to a fourth radiator arm.

28. The method of claim 27, further comprising tuning an electromagnetic
coupling of the third antenna structure and the first antenna structure
in the second frequency band, said electromagnetic coupling of the third
antenna structure and the first antenna structure being effected at least
in part by a first linear slot disposed substantially longitudinally
within the first radiator aim and a second linear slot disposed
substantially longitudinally within the second radiator arm.

29. The method of claim 28, further comprising tuning an electromagnetic
coupling of the fourth antenna structure and the second antenna structure
in the second frequency band, said electromagnetic coupling of the third
antenna structure and the first antenna structure being effected at least
in part by a third linear slot disposed substantially longitudinally
within the third radiator arm and a fourth linear slot disposed
substantially longitudinally within the fourth radiator arm.

30. The method of claim 27, further comprising: effecting electric
coupling of the first antenna structure to the feed via a first
conductive element disposed therebetween; effecting electromagnetic
coupling of the first radiator arm and the feed via a first
electromagnetic coupling element disposed electrically between the first
conductive element and third antenna structure; and effecting
electromagnetic coupling of the second radiator arm to the feed via a
second electromagnetic coupling element disposed electrically between the
first conductive element and the third antenna structure.

31. The method of claim 26, further comprising: exciting a fifth antenna
structure disposed substantially on the first side and
electromagnetically coupled to the second antenna structure in order to
radiate in the first frequency band; and exiting a sixth antenna
structure disposed substantially on the second side and
electromagnetically coupled to the first antenna structure, in order to
radiate in the first frequency band.

Description:

COPYRIGHT

[0001] A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright owner has
no objection to the facsimile reproduction by anyone of the patent
document or the patent disclosure, as it appears in the Patent and
Trademark Office patent files or records, but otherwise reserves all
copyright rights whatsoever.

FIELD OF THE INVENTION

[0002] The present invention relates generally to antenna apparatus for
use within electronic devices such as wireless radio devices, and more
particularly in one exemplary aspect to a multi-band long term evolution
(LTE) antenna, and methods of tuning and utilizing the same.

DESCRIPTION OF RELATED TECHNOLOGY

[0003] Increased proliferation of long term evolution and long term
evolution advanced (hereinafter collectively "LTE") mobile data services
creates an increased demand for compact multi-band antennas typically
used in radio devices, such as wireless access point, bridge, or a hub.
Typically, it is desired for an LTE-compliant radio device to support
operation in multiple frequency bands (such as, for example, 698 MHz to
960 MHz, 1710 MHz to 1990 MHz, 2110 MHz to 2170 MHz, and 2500 MHz to 2700
MHz). Furthermore, LTE system has been defined to accommodate paired
spectrum for Frequency Division Duplex (FDD) mode of operation where the
uplink and the downlink transmissions occupy different parts of the
spectrum. By way of example, the uplink occupies the frequency range from
1710 MHz to 1770 MHz, and the downlink occupies the frequency range from
2110 MHz to 2170 MHz. It is therefore desirable for antennas used in an
LTE-compliant device to cover a wide range of frequencies ranging from
about 650 MHz to about 2700 MHz, while maintaining a unidirectional
radiation pattern. It is further desired to be able to tune individual
operating frequency bands of the antenna without affecting antenna
functionality in other bands.

[0004] Dipole type antennas are typically used to achieve an
omni-directional radiation pattern, such as characterized by radiation
pattern that is shaped like a toroid in three-dimensional space and is
symmetric about the axis of the dipole.

[0005] However, most existing single feed dipole antenna solutions operate
in a single frequency band. At present, implementing a single planar
dipole antenna that is efficient in several frequency bands is
problematic, as separate antenna elements that cover different frequency
bands interact with each other and create mutual interference patterns
that degrade antenna performance. Some existing approaches attempt to
solve this problem by constructing multiple separately fed dipole
antennas, each cooperating in a separate frequency band. Multiple dipole
antennas (packaged within the same protective enclosure, also referred to
as the radome) are often used to achieve multiband operation. However,
such solutions require a separate feed for each antenna thereby
increasing cost and complexity. This approach may also cause coupled
resonances that adversely affect antenna performance.

[0006] Accordingly, there is a salient need for an improved multiband
dipole antenna solution suitable for use in, inter alia, LTE compliant
radio devices, that offers a lower cost and complexity, and provides for
improved control of antenna resonance. Such improved solution would also
ideally have a desirable form factor (e.g., small size, and compatible
with target applications such as hand-held mobile devices).

SUMMARY OF THE INVENTION

[0007] The present invention satisfies the foregoing needs by providing,
inter alia, a space-efficient multiband antenna apparatus, and methods of
tuning and use.

[0008] In a first aspect of the invention, an antenna apparatus operable
in a first frequency band and a second frequency band is disclosed. In
one embodiment, the antenna apparatus includes a dielectric element
comprising a first side and a second side, a feed point disposed on the
first side, and a ground point disposed on the second side, a first
structure operable in the first frequency band and disposed substantially
on the first side, a second structure operable in the first frequency
band and disposed substantially on the second side, a third structure
operable in the second frequency band and disposed substantially on the
first side, and a fourth structure operable in the second frequency band
and disposed substantially on the second side. In one variant, the first
structure is galvanically coupled to the feed point, the second structure
is galvanically coupled to the ground point, the third structure is
configured to electromagnetically couple to the first structure, and the
fourth structure is configured to electromagnetically coupled to the
second structure.

[0009] In another variant, the first structure includes a first radiator
arm disposed substantially co-planar yet parallel to a second radiator
arm and the second structure includes a third radiator arm disposed
substantially co-planar yet parallel to a fourth radiator arm, the first
radiator arm and the second radiator arm each comprise a linear slot
disposed substantially longitudinally within the respective aim, and the
apparatus includes a first substantially linear conductive element
disposed on the first side and configured to couple the feed point to the
first and the second radiator arms via a first T-junction, and a second
substantially linear conductive element disposed on the second side and
configured to couple the feed point to the third and the fourth radiator
arms via a second T-junction.

[0010] In another variant, the antenna apparatus includes a first
conductive element disposed between the first structure and the feed
point and effecting the galvanic coupling to the feed point, a first
electromagnetic coupling element electrically disposed between the first
conductive element and a first branch of the third structure, and a
second electromagnetic coupling element electrically disposed between the
first conductive element and a second branch of the third structure, so
that the first electromagnetic coupling element is configured to
electromagnetically couple the first branch of the third structure to the
feed point, and the second electromagnetic coupling element is configured
to electromagnetically couple the second branch of the third structure to
the feed point.

[0011] In yet another variant, the antenna apparatus includes a second
conductive element disposed between at least a portion of the second
structure and the ground point and effecting the galvanic coupling to the
ground point, a third electromagnetic coupling element electrically
disposed between at least a portion of the second conductive element and
a first branch of the fourth structure, and a fourth electromagnetic
coupling element electrically disposed between at least a portion of the
second conductive element and a second branch of the fourth structure,
the third electromagnetic coupling element is configured to
electromagnetically couple the first branch of the fourth structure to
the ground point, and the fourth electromagnetic coupling element is
configured to electromagnetically couple the second branch of the fourth
structure to the ground point.

[0012] In still another variant, the antenna apparatus includes a
structure disposed substantially on the first side and configured to
electrically couple to the second conductive element, so that electric
coupling of the structure to the second conductive element is effected
via a conductor configured to penetrate through the dielectric element in
a direction normal to the first side.

[0013] In another variant, the first structure and the second structure
are configured to cooperate to form at least a portion of a first dipole
antenna operable in the first frequency band, and the third structure and
the fourth structure are configured to cooperate to form at least a
portion of a second dipole antenna operable in the second frequency band
so that the antenna apparatus is characterized by a substantially
omni-directional radiation pattern in at least one of the first frequency
band and the second frequency band in a plane substantially normal to the
element, and the first frequency band includes a lower frequency long
term evolution (LTE) application band, and the second frequency band
includes an upper frequency LTE application band.

[0014] In another aspect of the invention, a multiband antenna component
for use with a radio communications device, the device operable in a
first frequency band and a second frequency band is disclosed. In one
embodiment, the antenna component includes a dielectric element
comprising a first side and a second side, a first structure operable in
the first frequency band and disposed substantially on the first side, a
second structure operable in the first frequency band and disposed
substantially on the second side, the first structure is connected to a
feed disposed on the first side, and the second structure is connected to
a coupling.

[0015] In one variant, antenna component includes a third structure
operable in the second frequency band and disposed substantially on the
first side, and a fourth structure operable in the second frequency band
and disposed substantially on the second side, the third structure is
configured to electromagnetically couple to the first structure, the
fourth structure is configured to electromagnetically couple to the
second structure, the first frequency band includes a lower frequency
long term evolution (LTE) application band and second frequency band is
selected from a group consisting of (i) 1710-1990 MHz, (ii) 2110-2170
MHz; and 2500-2700 MHz long term evolution (LIE) application frequency
bands.

[0016] In another variant, the first structure includes a first radiator
arm disposed substantially co-planar yet parallel to a second radiator
arm, the first radiator arm includes a first linear slot disposed
substantially longitudinally within the first radiator arm, the second
structure includes a third radiator arm disposed substantially co-planar
yet parallel to a fourth radiator arm, and the second radiator arm
includes a second linear slot disposed substantially longitudinally
within the second radiator arm, a first conductive element disposed
between the first structure and the feed and effecting the connection of
the first structure to the feed.

[0017] In another variant, the antenna component includes a first
electromagnetic coupling element electrically disposed between the first
conductive element and a first branch of the third structure, and a
second electromagnetic coupling element electrically disposed between the
first conductive element and a second branch of the third structure, the
first electromagnetic coupling element is configured to
electromagnetically couple the first radiator arm to the feed point, and
the second electromagnetic coupling element is configured to
electromagnetically couple the second radiator arm to the feed.

[0018] In yet another variant, the antenna component includes a first
conductive element disposed on the first side and configured to effect
the connection between the feed and the first structure, a second
conductive element disposed on the second side and configured to effect
the connection between the coupling and the second structure, and a
structure disposed substantially on the first side and configured to
electrically couple to the second conductive element.

[0019] In still another variant, outer perimeter of the first structure is
configured substantially external to outer perimeter of the second
structure, outer perimeter of the third structure is configured
substantially external to outer perimeter of the fourth structure, outer
perimeter of the first structure is configured to overlap at least
partially outer perimeter of the third structure when viewed in a
direction substantially normal to the first side, and outer perimeter of
the second structure is configured to overlap at least partially outer
perimeter of the fourth structure when viewed in the direction
substantially normal to the first side.

[0020] In a third aspect of the invention, a method of operating an
antenna apparatus is disclosed. In one embodiment, the method comprises
providing a feed signal to both a feed disposed on a first side of a
dielectric substrate, and to a coupling disposed on the second side of
the dielectric substrate; exciting a first antenna structure disposed
substantially on the first side and electrically coupled to the feed
point so as to radiate in a first frequency band; and exciting a second
antenna structure disposed substantially on the second side so as to
radiate in the first frequency band.

[0021] In a fourth aspect of the invention, a method of tuning an antenna
apparatus is disclosed. In one embodiment, the method comprises providing
a feed signal to both a feed disposed on a first side of a dielectric
substrate, and to a coupling disposed on the second side of the
dielectric substrate; exciting a first antenna structure disposed
substantially on the first side and electrically coupled to the feed so
as to radiate in a first frequency band, and exciting a second antenna
structure disposed substantially on the second side so as to radiate in
the first frequency band, and tuning an electromagnetic coupling of a
third antenna structure and the first antenna structure in a second
frequency band. In one variant, the electromagnetic coupling of the third
antenna structure and the first antenna structure is effected by a first
linear slot disposed substantially longitudinally within a first radiator
arm, and a second linear slot disposed substantially longitudinally
within a second radiator arm.

[0022] In a fifth aspect of the invention, a method of operating a mobile
device is disclosed. In one embodiment, the method comprises providing a
feed signal to both an antenna feed disposed on a first side of a
dielectric substrate, and to an antenna coupling disposed on the second
side of the dielectric substrate; exciting a first antenna structure
disposed substantially on the first side and electrically coupled to the
feed so as to radiate in the first frequency band; and exciting a second
antenna structure disposed substantially on the second side to radiate in
the first frequency band.

[0023] Further features of the present invention, its nature and various
advantages will be more apparent from the accompanying drawings and the
following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The features, objectives, and advantages of the invention will
become more apparent from the detailed description set forth below when
taken in conjunction with the drawings, wherein:

[0025] FIG. 1 illustrates top and bottom elevation views of a multiband
dipole antenna structure according to a first embodiment of the
invention.

[0026] FIG. 1A illustrates top and bottom elevation views of a multiband
dipole antenna structure according to a second embodiment of the
invention.

[0027] FIG. 1B illustrates top and bottom elevation views of a multiband
dipole antenna structure according to a third embodiment of the
invention.

[0028] FIG. 1C is a top elevation view showing a multiband dipole antenna
of FIG. 1B, configured in a radome according to one embodiment of the
invention.

[0029] FIG. 2 is a plot of measured free space input return loss of the
exemplary multiband dipole antenna of the embodiment of FIG. 1B.

[0030]FIG. 3 is a plot of measured total efficiency of the exemplary
multiband dipole antenna of the embodiment of FIG. 1B.

[0031] FIG. 4 is a plot of measured maximum antenna gain of the exemplary
multiband dipole antenna of the embodiment of FIG. 1B.

[0032]FIG. 5 is a diagram illustrating an exemplary coordinate system
used in radiation pattern measurements.

[0037] Reference is now made to the drawings wherein like numerals refer
to like parts throughout.

[0038] As used herein, the terms "access point," "wireless hub," "wireless
bridge", `wireless station", and "corporate access point" refer without
limitation to any wireless radio device capable of exchanging data via a
radio link.

[0039] As used herein, the terms "antenna," "antenna system," "antenna
assembly", and "multi-band antenna" refer without limitation to any
system that incorporates a single element, multiple elements, or one or
more arrays of elements that receive/transmit and/or propagate one or
more frequency bands of electromagnetic radiation. The radiation may be
of numerous types, e.g., microwave, millimeter wave, radio frequency,
digital modulated, analog, analog/digital encoded, digitally encoded
millimeter wave energy, or the like.

[0040] As used herein, the terms "board" and "substrate" refer generally
and without limitation to any substantially planar or curved surface or
component upon which other components can be disposed. For example, a
substrate may comprise a single or multi-layered printed circuit board
(e.g., FR4), a semi-conductive die or wafer, or even a surface of a
housing or other device component, and may be substantially rigid or
alternatively at least somewhat flexible.

[0041] The terms "frequency range", "frequency band", and "frequency
domain" refer without limitation to any frequency range for communicating
signals. Such signals may be communicated pursuant to one or more
standards or wireless air interfaces.

[0043] Furthermore, as used herein, the terms "radiator," "radiating
plane," and "radiating element" refer without limitation to an element
that can function as part of a system that receives and/or transmits
radio-frequency electromagnetic radiation; e.g., an antenna or portion
thereof.

[0044] The terms "RF feed," "feed," "feed conductor," and "feed network"
refer without limitation to any energy conductor and coupling element(s)
that can transfer energy, transform impedance, enhance performance
characteristics, and conform impedance properties between an
incoming/outgoing RF energy signals to that of one or more connective
elements, such as for example a radiator.

[0045] As used herein, the terms "top", "bottom", "side", "up", "down",
"left", "right", and the like merely connote a relative position or
geometry of one component to another, and in no way connote an absolute
frame of reference or any required orientation. For example, a "top"
portion of a component may actually reside below a "bottom" portion when
the component is mounted to another device (e.g., to the underside of a
PCB).

[0047] The present invention provides, in one salient aspect, a multi-band
dipole antenna apparatus for use with a radio device which advantageously
provides reduced size and cost, and improved antenna performance. In one
embodiment, the antenna apparatus includes two separate antenna
assemblies disposed on the opposing sides of a thin dielectric element.

[0048] Each antenna assembly of the exemplary embodiment is adapted for
use in LTE devices, and includes a first radiator structure configured to
operate in a lower frequency band (LFB), a second radiator structure
configured to operate in an upper frequency band (UFB), and an
electromagnetic coupling element disposed there between. The first
radiator structure is configured such that a higher-order resonance mode
optimizes upper frequency band operation. The first radiator structure is
galvanically coupled to a feed port of the radio device via a
transmission line element. The second radiator structure is
electromagnetically coupled to the feed via the electromagnetic coupling
element, also commonly referred to as the parasitic coupling. The two
antenna assemblies are configured in an opposing fashion such that the
LFB radiator of the top antenna is positioned above the UFB radiator of
the bottom antenna and the UFB radiator of the top antenna is positioned
above the LFB radiator of the bottom antenna. Such radiator configuration
enables the UFB structure of each antenna assembly (for example, on the
top side) to couple to the LBF structure of the opposing antenna assembly
(for example, on the bottom side) via electric field coupling at a
resonance frequency across the dielectric substrate thickness.

[0049] The transmission line of each antenna assembly includes, in one
implementation, a linear microstrip element featuring a tuning flap
structure that may be disposed at different locations along the length of
the transmission line. Such configuration improves antenna feed
efficiency and optimizes antenna resonance.

[0050] In order to obtain dipole radiation pattern, each of the LFB and
UFB radiator structures of the exemplary embodiment includes a pair of
radiating arms, disposed symmetrically with respect to a longitudinal
axis of the dielectric element and parallel with respect to one another.
In one variant, the UFB arms are configured as elongated rhomboids and
UFB arms are configured as elongated rectangular or elliptical elements.
Such two planar blade dipole antenna assemblies provide a combined
omni-directional radiation pattern in the azimuthal plane for each of the
lower and upper frequency bands. A linear slot (disposed axially within
the LFB arm, in one implementation, is configured to improve HFB
coupling.

[0051] A single multi-feed transceiver is configured to provide feed
signal to both antenna assemblies. In one approach, the feed is effected
via a coaxial cable which is coupled to a top side of the antenna
apparatus. The antenna coupling structure (in one implementation)
includes a set of conductors galvanically coupling the top side coupling
point to the bottom side coupling point in order to provide feed to the
second antenna assembly.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0052] Detailed descriptions of the various embodiments and variants of
the apparatus and methods of the invention are now provided. While
primarily discussed in the context of the access point radio devices
useful with an LTE wireless communications device or system, the various
apparatus and methodologies discussed herein are not so limited. In fact,
many of the apparatus and methodologies described herein are useful in
any number of complex antennas, whether associated with mobile or fixed
devices, cellular or otherwise, that can benefit from the multiband
dipole antenna methodologies and apparatus described herein.

Exemplary Antenna Apparatus

[0053] Referring now to FIGS. 1 through 1C, various exemplary embodiments
of the radio antenna apparatus of the invention are described in detail.

[0054] It will be appreciated that while these exemplary embodiments of
the antenna apparatus of the invention are implemented using a blade
dipole (using two surface of a planar substrate) antenna (selected in
these embodiments for their desirable attributes and performance), the
invention is in no way limited to planar antenna configuration, and in
fact can be implemented using other shapes, such as, for example, a
three-dimensional (3D) cylinder or a truncated cone.

[0055] One exemplary embodiment of a multiband antenna component 100 for
use with a radio device is presented in FIG. 1, showing top and bottom
elevation views of the antenna structure. The antenna component shown in
FIG. 1 includes a planar dielectric element 102 fabricated from a
suitable material such as 4000-series high frequency circuit laminate
manufactured by Rogers Corporation, although it will be appreciated that
other materials may be used. The antenna 100 further includes two antenna
sub-assemblies 101, 131 disposed on the top and the bottom side of the
dielectric element 102, respectively. In another embodiment (not shown),
the antenna structure is fabricated using a flex circuit.

[0056] The top antenna sub-assembly 101 includes a low frequency band
(LFB) structure comprised of two symmetric arms 106, each coupled to a
feed 104 (here a point) via a linear transmission line element 110,
implemented as a microstrip in one variant. In another variant, a flap
114 is added to the transmission line in order to enable precise
manipulation of antenna resonances, and to improve feed coupling. In one
approach, the flap 114 includes a rectangular perimeter, while other
shapes (such as rhomboid, circle or an ellipse) are equally compatible
and useful with the invention. Furthermore, positioning the flap 114 at
different locations along the transmission line 110 allows for
optimization of antenna operation in different LF and HF bands.

[0057] The feed 104 and the ground 120 coupling points are configured to
connect the antenna component 100 via a feed cable to the device feed
engine. In one implementation, the feed cable includes a coaxial cable
with a shield, and is connected to the radio device via an RF connector.
Other 50 ohm RF transmission line configurations, e.g., SMA connector,
flex circuit, etc. are usable as well. The feed conductor of the coaxial
feed cable connects the antenna feed point 104 to the RF engine feed
port, and the shield conductor is connected to the antenna ground
coupling point 120. The antenna ground coupling structure includes the
top ground point 120 connected to the bottom ground structure 134
through, for example, via holes that provide galvanic contact between the
two ground structures (120, 134), therefore coupling the structure 134 to
the feed cable ground conductor.

[0058] The bottom antenna sub-assembly 131 similarly includes a low
frequency band structure comprised of two symmetric arms 136, each
coupled to the ground structure 134 via the transmission line element
140. In one variant, a flap 144 is added to the transmission line 140 in
order to enable precise manipulation of antenna resonances, and to
improve feed coupling. In one approach, the flap 114 comprises a
rectangular perimeter, while other shapes (such as rhomboid, circle or an
ellipse) are equally compatible and useful with the invention.
Furthermore, positioning the flap 114 at different locations along the
transmission line 110 allows for optimization of antenna operation in
different LF and HF bands.

[0059] Each of the top and the bottom antenna sub-assemblies 101, 131
comprises a high frequency band (HFB) radiating structure comprising a
pair of arms 112, 142, respectively. The arms 112 are disposed
symmetrically with respect to the transmission line 110 while the arms
142 are disposed substantially symmetrically with respect to the
longitudinal axis 117 of the antenna assembly. The HFB arms 112 are
electromagnetically coupled to the feed via nonconductive gaps 108,
formed between the adjacent edges of the HFB arms 112 and the
transmission line 110 (and its "T" junction portion). The gaps 108 act as
electromagnetic coupling elements, providing capacitive coupling between
the transmission line and the HFB arms, and enabling energy transfer from
the feed.

[0060] Similarly, the HFB arms 142 are electromagnetically coupled to the
feed via nonconductive gaps 109 formed between the adjacent edges of the
HFB arms 142 and the T-junction portion of the transmission line 110. The
gaps 109 act as electromagnetic coupling (also referred to as the
parasitic coupling) elements, enabling higher-order mode resonances in
the HFB arms. The configuration shown in FIG. 1 causes the lower band
feed (for example, in the frequency range between 700 MHz and 960 MHz) to
generate second-order resonance modes in the HFB arms, thereby
facilitating antenna operation in a higher frequency range (for example,
between 1710 and 2170 MHz). Note, although the second harmonic for an
ideal (properly matched) single frequency oscillator of 960 MHz
corresponds to 1920 MHz, the wide span of the low frequency range
(700-960 MHz) enables efficient antenna operation at frequencies of up to
2170 MHz in the HFB.

[0061] As shown and described with respect to FIG. 1, the LFB 106, 136 and
the HFB 112, 136 radiating structures are disposed opposing each other on
the top 101 and the bottom 131 antenna sub-assemblies, respectively. That
is, the LFB structure 106 is disposed above the HFB structure 142, while
the HFB structure 112 is disposed above the LFB structure 136. This
"head-to-toe" configuration further enables coupling of the HFB
structures 112, 142 to the respective LFB structures 106, 136,
respectively, via electric field at the resonance across the thickness of
the dielectric substrate 102. The electromagnetic and electric field
coupling described above is also commonly referred to as "parasitic
coupling", and the antenna elements that are fed in such manner are
commonly referred to as "parasitics".

[0062] Each of the LFB arms 106, 146 of the antenna embodiment of FIG. 1
comprises a linear slot 116 disposed axially proximate the center axis of
the respective arm, so as to improve electromagnetic coupling efficiency
of the respective HFB arm (that is the arms 142, 112, respectively)
disposed underneath the LFB arms 106, 146.

[0063] In the embodiment of FIG. 1, In order to increase antenna
bandwidth, the antenna sub-assemblies 101, 131 comprise a second set of
lower band parasitically coupled radiator arms 118, 148 configured
opposite from the LFB respective structures. That is, the parasitic LFB
structure 118 of the top sub-assembly 101 is disposed above the LFB
structure 136 of the bottom sub-assembly 131, and the parasitic LFB
structure 148 of the bottom sub-assembly 131 is disposed above the LFB
structure 106 of the top sub-assembly 101, respectively. Such antenna
sub-assembly configuration causes electromagnetic coupling between the
parasitic LBF structures 118, 148 and the directly-fed LBF structures
106, 136, respectively, thereby enabling antenna matching over a wider
frequency band. This approach advantageously increases useful frequency
range of the antenna apparatus shown in FIG. 1, and enables radio device
operation in additional frequency bands (e.g., LTE bands).

[0064] The exact location and the shapes of each of the structures 106,
112, 118, 136, 142, 148 are configured with regard to a specific design
requirements such as available space, bandwidth, efficiency, radiation
pattern, and power. The exemplary antenna of the embodiment presented in
FIG. 1 is configured to operate in the following long-term evolution
(LTE)/LTE-A system frequency bands of approximately 698-960 MHz,
1710-1990 MHz, 2110-2170 MHz, and 2500-2700 MHz. In the antenna variant
shown in FIG. 1, the exemplary antenna is approximately 165 mm (6.56
inch) in length, 28 mm (1.1 inch) in width, and 0.9 mm (0.032 inch)
thick. In other variants (not shown), the antenna width is reduced to 25
mm (1 inch) or 20 mm (0.79 inch), while keeping the same length and
thickness.

[0065] Other embodiments of the invention configure the antenna apparatus
to cover WWAN (e.g., 824 MHz-960 MHz, and 1710 MHz-2170 MHz), and/or
WiMAX (2.3 and 2.5 GHz) frequency bands. Yet other frequency bands may be
achieved as desired, using variations in the configuration of the
apparatus.

[0066] The directly-fed LFB antenna arms (106, 136) of the exemplary
embodiment are configured as substantially diamond-shaped elongated
polygons. That is, the width of each of the arms 106, 136 is smaller than
the length. In the embodiment shown in FIG. 1, one end of each arm
features a tuning element 122, 150, and the other end (128) is truncated
to effect precise antenna tuning to the desired bands of operation. The
radiator arm diamond shape provides good electromagnetic coupling to the
HFB arms, and produces a wide band response in the lower frequency band.

[0067] Another exemplary embodiment of the dipole antenna according to the
present invention is shown in FIG. 1A. The antenna component 158 of this
embodiment includes a top sub-assembly 159 and a bottom sub-assembly 161,
each configured similarly to the antenna sub-assemblies 101, 131 of the
device of FIG. 1 described supra. In the embodiment of FIG. 1A, one end
of each arm of the directly-fed LFB structure 162, 166 features a
triangular-shaped tuning element (similar to the element 122 of the
embodiment of FIG. 1), and the opposing end of the arm features a
trapezoidal-shaped tuning element 168, each configured to effect antenna
tuning to the desired bands of operation.

[0068] It is appreciated by those skilled in the art that a multitude of
other antenna radiating structures are equally compatible and useful with
the present invention such as, inter alia, the LFB radiators shaped as
shown in the antenna embodiment of FIG. 1B. The antenna component 170 of
this embodiment includes a top sub-assembly 171 and the bottom
sub-assembly 172, each configured similarly to the antenna sub-assemblies
101, 131 of FIG. 1 described supra. In the embodiment of FIG. 1B, each
arm 174, 176 of the direct-fed LFB structures is shaped as a rhomboid
with a triangular-shaped tuning element 178 (similar yet smaller compared
to the element 122 of the embodiment of FIG. 1) disposed on one end, that
is proximate to the direct connection to the transmission lines 110, 140.

[0069] An embodiment of the antenna apparatus, comprising multiband dipole
antenna components (such as shown and described with respect to FIGS.
1-1B, supra) is presented in FIG. 1C in the form of a "radome". The
antenna apparatus 180 of FIG. 1C includes the antenna component (such as,
for example, the component 170 of FIG. 1B) encapsulated in a radome
structure 182. The top antenna sub-assembly 171 of FIG. 1B is shown in
white, and portions of the bottom antenna sub-assembly 172 of FIG. 1B are
shown in black in FIG. 1C. One end of the antenna apparatus 180 features
a mounting flange 184, which is used to attach the antenna during
operation and to route a feed cable 186.

[0070] The radome structure 182 is preferably fabricated using
thermoplastic materials such as e.g., polycarbonate (PC), or
Acrylonitrile Butadiene Styrene (ABS). The radome 182 provides mechanical
support for the antenna radiating elements and protection from the
elements during use. As the radome 182 affects RF field distribution and
antenna resonance frequency, tuning of the antenna assembly (that uses
the exact radome structure of the final product) is required.

[0071] In the antenna embodiments shown and described above with respect
to FIGS. 1-1C, antenna feed couplings are disposed proximate one lateral
edge of the dielectric substrate. To facilitate antenna mounting and
coupling to the feed cable, both coupling structures (such as the feed
point 104 and the ground coupling point 120) are disposed on the same
side of the substrate. Such coupling configuration simplifies attachment
of the RF feed cable to the antenna sub-assemblies, and optimizes antenna
resonances with different connector types. In one variant, the feed cable
is attached to the dipole antenna component using an RF connector, or a
mechanical friction joint (crimp, push and lock), or any other suitable
technology.

[0072] It is appreciated by those skilled in the arts that the above feed
coupling configuration is merely exemplary, and other implementations are
usable as well, such as for example soldering the feed conductor to the
top sub-assembly and the ground conductor to the bottom sub-assembly.

[0073] The exemplary antenna embodiments shown and described with respect
to FIGS. 1-1C, supra, utilize a single feed antenna configuration such
that the antenna radiators of one band (for example the lower band) are
fed directly via a feed strip (the transmission line 110), and the
antenna radiators of a second bands (HFB) are fed by way of
electromagnetic coupling. The top antenna sub-assembly (such as, for
example, the sub-assembly 101 of FIG. 1) is connected to the feed
conductor of the radio device and acts as one arm of the dipole, while
the bottom antenna sub-assembly (such as, for example, the sub-assembly
131 of FIG. 1) is connected to the ground conductor, and acts as a ground
base arm of the dipole.

[0074] The exemplary antenna configuration (such as that shown in FIG. 1)
includes two side-by-side dipoles in a vertical plane that are combined
by the transmission line (110), thus providing the desired
omni-directional antenna radiation pattern in azimuthal plane, as
illustrated by the antenna performance results described below.

Performance

[0075] Referring now to FIGS. 2 through 8-11, performance results obtained
during testing by the Assignee hereof of an exemplary antenna apparatus
constructed according to the invention are presented.

[0078] An efficiency of zero (0) dB or 100% corresponds to an ideal
theoretical radiator, wherein all of the input power is radiated in the
form of electromagnetic energy. The data in FIG. 3, shown both in dB
(solid line) and in % (vertical bars), are collected in the following
frequency bands: (i) the lower band 698-960 MHz; (ii) the first upper
band 1710-1980 MHz; (iii) the second upper band 2110-2170 MHz, and (iv)
the third upper band 2500-2700 MHz, denoted with the designators 302-308,
respectively. The data of FIG. 3 demonstrate LFB efficiency between 65%
and 90% in a lower portion of the lower band, decreasing to 40% level at
the upper edge of the LFB. The first upper band (304) efficiency is above
60% throughout the band, and the second upper band has efficiency between
35% and 70%. The third upper band 308 shows efficiency in a range between
30% and 70%. These results confirm that the antenna HFB radiating
elements configuration (such as, for example structures 112, 142 of FIG.
1) enables tuning of the HFB separately from the LFB, and demonstrate
that an antenna structure according to the invention advantageously
enables simultaneous antenna operation in several different frequency
bands over a frequency range that is wider than supported by presently
available antenna solutions of similar sizes.

[0079] FIG. 4 presents data regarding measured maximum antenna gain
obtained with the same antenna configuration (FIG. 1B). The data in FIG.
4 confirm antenna gain between -0.5 and 3 dB in the LFB, 0 to 4 dB in the
first upper band, and 4 to 6 dB in the second upper band.

[0080] FIGS. 5 through 8-11 present data related to measured radiating
pattern of the exemplary multiband dipole antenna configured in
accordance with the embodiment of FIG. 1B. FIG. 5 illustrates an
exemplary coordinate system and definitions useful for interpreting the
radiating patterns of FIGS. 6-1 through 8-11. In FIG. 5, θ is the
elevation angle, φ is the azimuth angle, and the x-y plane
(θ=90 deg.) corresponds to the azimuth plane. The azimuth plane
radiation patterns are obtained with measurements made while traversing
the entire x-y plane around the antenna under test. The elevation plane
in FIG. 5 is defined as a plane orthogonal to the x-y plane. The
elevation plane with the angle φ=90 deg corresponds to the y-z plane,
while the elevation plane with the angle φ=0 deg. corresponds to the
x-z plane. The elevation plane patterns are obtained traversing the
entire y-z plane around the antenna under test. The above definitions are
used in describing exemplary antenna radiation patterns with respect to
FIGS. 6-8, described below.

[0083] The radiation patterns 602-616 of FIGS. 6-1 through 6-11 and
702-716 of FIGS. 7-1 through 7-10 demonstrate a typical dipole antenna
radiation pattern, with the maximum power achieved at elevation angles of
90 and 270 deg, as expected. While the radiation patterns 618-622 and
718-720 obtained at the highest frequencies (2500 MHz, 2600 MHz, and 2700
MHz, respectively) show noticeable deviations from the dipole behavior,
they provide sufficient performance in most typical operational
conditions.

[0085] The data presented in FIGS. 2-4 and FIGS. 6-1 through 8-11 confirm
that a single planar dipole antenna, configured in accordance with the
invention, is capable of efficient operation in the LTE frequency ranges
of 698-960 MHz, 1710-1980 MHz, 2110-2170 MHz, and 2500-2690 MHz,
providing omni-directional radiation with a gain of 2 dBi, a level of
performance that is unattainable with prior art single-feed dipole
antenna solutions. Such capability provided by the present invention
advantageously allows operation of a radio frequency device (such as a
corporate wireless access point, wireless bridge or a wireless hub) with
a single antenna over several mobile frequency bands such as GSM710,
GSM750, GSM850, E-GSM900 GSM810, GSM1900, GSM1800, PCS-1900, as well as
LTE/LTE-A and WiMAX (IEEE Std. 802.16) frequency bands. As persons
skilled in the art will appreciate, the frequency band composition given
above may be modified as required by the particular bands of the
application(s), and additional bands may be supported/used as well.
Furthermore, the electrical dimensions of an antenna configured in
accordance with the invention can be scaled (up or down) in order to move
operating bands of interest down/up, respectively. For example, if
antenna dimensions are increased by a factor of two (compared to the
embodiment of FIG. 1B), the corresponding operating frequency bands are
scaled down by the same factor producing an antenna operating in a
frequency range from about 350 MHz to about 1350 MHz. Similarly, an
antenna that is half the size of the antenna of FIG. 1B will operate in a
frequency range from about 1400 MHz to about 5400 MHz.

[0086] Advantageously, an antenna apparatus configuration comprising
planar dipole antenna components as in the illustrated embodiments
described herein allows for optimization of antenna operation in the
lower frequency band simultaneously with the upper band operation. This
antenna solution allows for, inter aria, a single standards-compliant
(e.g., LTE-compliant) wireless device (such as a corporate access point,
and back up for wireless link for data service) to cover several relevant
frequency bands, while maintaining an improved dipole-type radiation
pattern for most of the frequency range. This capability advantageously
enables, among other things, fourth generation wireless (4G) swivel blade
antennas for hubs, access points, routers and small base station, and
femto-cell 4G applications.

[0087] In addition, the use of the exemplary single-feed configuration
simplifies antenna connections, and allows for a smaller and less
complicated design of the device RF feed electronics.

[0088] In one implementation of the invention, an external antenna is
employed to establish a small corporate access point and a backup
wireless link for data service, and to serve established external antenna
demand in LTE applications.

[0089] It will be recognized that while certain aspects of the invention
are described in terms of a specific sequence of steps of a method, these
descriptions are only illustrative of the broader methods of the
invention, and may be modified as required by the particular application.
Certain steps may be rendered unnecessary or optional under certain
circumstances. Additionally, certain steps or functionality may be added
to the disclosed embodiments, or the order of performance of two or more
steps permuted. All such variations are considered to be encompassed
within the invention disclosed and claimed herein.

[0090] While the above detailed description has shown, described, and
pointed out novel features of the invention as applied to various
embodiments, it will be understood that various omissions, substitutions,
and changes in the form and details of the device or process illustrated
may be made by those skilled in the art without departing from the
invention. The foregoing description is of the best mode presently
contemplated of carrying out the invention. This description is in no way
meant to be limiting, but rather should be taken as illustrative of the
general principles of the invention. The scope of the invention should be
determined with reference to the claims.